The present invention relates to an analog-digital control device and more particularly to a control device having a memory with multiple, readily accessible, selectable access ports to allow the control device to be quickly reprogrammed by unskilled personnel and thus render the control device particularly useful for the laboratory environment.
The present invention has found particular application in the field of measuring the absorbency of various absorbent materials of the kind that would be used in disposable diapers, bandages, sanitary napkins, incontinent pads and the like. During use there is often a compression load on such devices, for example, a baby might be sitting on the diaper or a bandage might be wound with some tightness about the body. Therefore, when one is testing the absorbency of a particular material, it is useful to place a compression load on the material and to vary the load according to specific time sequences or other parameters. The absorbency data collected under these conditions will more accurately reflect actual use.
When one is actually testing the absorbency of such material in a laboratory, it is useful to be able to load the material with a prescribed load for a prescribed period of time and to record the data automatically. Especially in the laboratory environment, it is useful to be able to quickly and easily change the applied loads and the time sequences without having to waste valuable laboratory time in resetting the test apparatus.
In the past, such tests had been conducted by a laboratory technician who would place a known weight on a test sample of absorbent material and observe the sample and measure its thickness at regular time intervals. There is a correlation between the thickness and absorbency of the test sample as pointed out in the testing procedure that is employed by a Gravimetric Absorption Tester, described in U.S. patent application Ser. No. 149,214 filed on the same day as this application by Wesley J. McConnell, and assigned to the same assignee of this application. The said McConnell application is incorporated herein by reference.
It would be desirable to have a control circuit for a testing apparatus which would be capable of applying a desired load for a desired period of time and for automatically recording the load actually applied to the sample and for recording the thickness of the sample.
Present analog-digital control circuits are capable of generating a prescribed analog signal for a prescribed variable time periods. Available microprocessor units could be used for such a purpose. However, such microprocessor units are usually sequentially accessible according to a set computer program. If the operator wishes to change any of the input parameters, particularly the prescribed time periods, it is necessary to access the microprocesser at the correct address location, erase existing memory and reprogram the microprocesser according to the new time sequence. This reprogramming can take a significant amount of valuable laboratory time and can usually only be accomplished by a skilled computer programmer.
The time input could also be readily varied by using a number of sequenced timers. This would give ready access to the time input parameter by an unskilled lab technician, but existing timers do not provide for the large variety of time ranges that are sometimes necessary for laboratory applications.
What is needed is a analog-digital control circuit which may be readily and quickly reprogrammed by an unskilled laboratory technician so that test apparatus will have a large variety of input control parameters particularly suited for the laboratory environment.